Behind the scenes

Though the question on Pottermore's sorting quiz regarding this cure does not specify which Headmaster was supposedly creating it, it is most likely intended to be Albus Dumbledore, as the hypothetical scenario posed by the question seem to be intended to take place around the time of the sorting in 1991, as the Hogwarts student records also mentioned in this question are supposed to be 1000 years old. Of course, as the scenario is hypothetical, it is possible this cure, at least as created by a Hogwarts Headmaster, does not exist at all.